It is generally well known in the art to fabricate containers by the process of blow molding, wherein a plastic parison known as a “preform” is molded into a container. This preform is generally provided in the form of an elongated tube which defines a preform cavity and which is provided with a closed distal end and a mouth at an open proximal end in communication with the preform cavity.
During the molding process, the preform is placed in a mold which defines a mold cavity with the form of a container. The mold is provided in at least two segments, ideally configured such that the open proximal end of the preform protrudes from the mold while a majority of the preform remains within the mold cavity. A pressurized fluid is then injected into the preform cavity, which induces it to expand. The preform is thus expanded into the contours of the mold, forming a container.
Advantageously, a stretching rod is also employed during the molding process: during the injection of the pressurized fluid a rigid rod is inserted into the mouth of the preform along a longitudinal axis of the latter so as to contact the interior surface of the closed end, and then further advanced to induce the preform to plastically deform along its longitudinal axis. By controlling the rate of advancement of the stretching rod and the rate of injection of the pressurized fluid, one may exercise a great deal of control over the expansion of the preform. The containers so produced are thus generally of high quality and consistency.
The apparatuses carrying out this process generally comprise an injection head, which includes a nozzle to establish fluid communication between the mouth of the preform and a fluid supply; a valve or valves for controlling the flow of the fluid from the injection head to the cavity of the preform; the stretching rod, arranged coaxially with and mobile relative to the nozzle; and various channels for conducting the pressurized fluid from the fluid supply to the cavity of the preform. The stretching rod, in particular, is configured so as to extend and retract from the injection head during the operation of the injection apparatus.
Traditionally, the pressurized fluid utilized to expand the preform into a container is pressurized air; after being formed, the containers are removed for filling on a separate apparatus. However, it has recently become known to inject a liquid product into the preform, the liquid product remaining in the resulting container and being sealed therein for distribution. This is desirable in that a container is thereby formed and filled in a single step by a single machine, realizing considerable economies of space and time in its production.
However, it is very important to maintain the injection head at a high level of cleanliness, especially where the containers being fabricated are filled with a food, beverage, medicine, or other perishable product. It is moreover especially important to maintain the stretching rod in a high state of cleanliness; the stretching rod is inserted into the container, and thus could potentially insert microorganisms or other contaminants directly into the container if its cleanliness is not assiduously maintained.
This is problematic, in that cleaning, and maintaining the cleanliness of, the molding apparatuses known in the art is difficult. In particular, the environment within the injection head may become such that it promotes the growth of microorganisms upon the stretching rod, the stretching rod being retracted into the injection head at the end of each container fabrication cycle.
Cleaning the stretching rod is difficult, in that it requires one to halt the production of containers and extend the stretching rod from the injection head so that it may be cleaned. Depending on the design of the injection head, it may even be necessary to dismantle and disassemble the injection head to fully clean the stretching rod to an acceptable degree.
It is thus an objective of this invention to furnish an injection head for a container-fabricating apparatus which may be quickly, easily, and economically cleaned, as well as a method for performing such cleaning.